Defer loading of Net:SSLeay, to prevent segfaults under mod_perl

Plack::Handler::Apache2 removes $ENV{MOD_PERL}, to prevent some modules
(like CGI and CGI::Cookie) from looking in the wrong locations for
input.  Unfortunately, this has catastrophic results for the loading of
Net::SSLeay, which segfaults Apache if loaded under mod_ssl + mod_perl
without being able to detect it is running as such.

Remove the early loading of Net::SSLeay, and the entire
ExternalServiceUsesSSLorTLS argument in general.  There is no need to
load Net::SSLeay early, and no need for a configuration variable that
merely repeats what can be inferred from individual service
configurations.
Standardize and modernize POD

Remove the documentation dealing with the no-longer-supported 3.4, 3.6,
and 3.8 releases.  Use the standard RT::Extension installation
instructions, as well as footer.  Condense the "MORE ABOUT THIS MODULE"
into the "DESCRIPTION" and de-duplicate, removing reference to the
no-longer-relevant RT::Authen::CookieAuth.
Move configuration documentation into the main file

This condenses and updates the configuration options, as well as
providing them in one place.
Version 0.22_01 releng